JPS58106203A - Hydraulic controller - Google Patents

Abstract

PURPOSE:To control the discharge amount of a variable displacement pump to the min. necessary flow-rate as required in each case independently of the number of revolution of an engine during idling or traveling and control the discharge amount of the pump to the max. flow-rate corresponding to the number of revolution of the engine during operation. CONSTITUTION:The oil discharged from a pump 2 flows into a tank 11 through a throttle 3 during idling, and an excess flow-rate signal is input into a calculator 28 through a flow-rate meter 26 to control the discharge amount of the pump to the min. necessary flow-rate. Although the pressures at both edges of the throttle 3 increase during traveling, the differential pressure is constant, and the discharge amount of the pump is controlled to a certain min. necessary flow- rate. In operation, selector valves 7a and 7b are switched to each operation position. Then, the value of the excess flow-rate signal of the flow meter 26 is reduced, and the calculator 28 outputs a tilt-angle increasing signal into a servomotor 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic control device for a hydraulic circuit of a forklift, a loader, etc., and more specifically, a variable displacement pump driven by an engine, and a system for controlling the discharge oil of the variable displacement pump. A 70-depider that flows through the first pipe line and the second pipe line and has a throttle on the first pipe side, a first actuator connected to the IIEI pipe line via a first switching valve, and a second pipe line. The present invention relates to a hydraulic control device in a hydraulic circuit having a second actuator connected to a road via a second switching valve.

FIG. 1 is a circuit diagram showing an example of a conventional hydraulic control device of this type, which is applied to a forklift. In FIG. 1, a fixed displacement pump %4#'i driven by the 2/d engine 1 is connected to a first conduit through which the oil discharged from this pump 2I flows through a restrictor 3'.

In this example, the tank IIK is communicated with through a neutral port of a power steering valve (first switching valve) 15 for operating a power steering cylinder (first actuator) 14. 5 is a second pipe branched from the upstream side of the throttle 3 via the papermaking pressure control valve 17, and is connected to the neutral port of the 1-work switching valve (second switching valve) 7a, 7b, and is connected to the neutral port of the 1-work switching valve 7m. , 7b is in neutral, its neutral port) 11 communicates with tank 11. Switch the work switching valves 7m and 7bd from the neutral position to the operating position and tilt cylinder 6&
A portion of the oil discharged from the pump 21 is supplied to the 7 actuators of 1lE2 such as the lift cylinder 6b and the lift cylinder 6b.
It is a round one that operates 6m and 6b. 16m, 1
6bFi' respectively when switching the switching valve 15 for power steering and the switching valve 7 for work.

This is a relief valve for releasing the surge pressure generated when switching 7b to tank IIK.

In such a conventional device Kkm, when the engine 1 is rotated, the fixed displacement pump 2I is driven.

When the switching valves 15.7m and 7b are not operated and they are in the neutral state, the oil discharged from the pump 21 flows into the tank 11 through the throttle 3 of the first pipe 4, and the differential pressure generated across the throttle 3 The pressure control valve 17 is activated, and a portion of the pump discharge oil flows into the tank 11 via the second pipe line 5 and the neutral ports of the switching valves 7a and Wb. When the forklift is traveling, the switching valve 15 is operated to operate the power steering cylinder 14. At this time, the oil discharged from the pump 21 is supplied to the power steering cylinder 14 through the throttle 3, and the pressure at both ends of the throttle 3 increases, but the differential pressure therebetween remains constant. Also, during one operation, the switching valve is 7m.

7b to operate the tilt cylinder 6a and lift cylinder 6.
Activate the second actuator such as b.

At this time, the flow rate required to operate each cylinder 6m and 6b is 1
12 and is supplied through conduit 5.

However, in such a conventional device, the required flow rate during work is the highest, and the discharge rate of the fixed displacement pump 21 is determined according to this. Not only is there a large amount of energy loss due to excess flow, but the flow rate during driving is less than half the pressure of the flow rate during work, and the
However, approximately 4 of the pump discharge amount becomes a surplus flow rate, and the energy loss due to this is quite large. Furthermore, in the case of a forklift, approximately half of the total working time is spent traveling, so it is extremely important to minimize energy loss during travel.

Therefore, the present invention uses a variable displacement pump as the pump driven by the engine, and controls the discharge amount of the variable displacement pump to the required minimum flow rate regardless of the engine speed during idling or running. However, it is an object of the present invention to provide a hydraulic control device that can control the pump discharge amount to a maximum flow rate depending on the engine rotation speed during work by supplying pump discharge oil.

The present invention, which achieves the above objects, will be described below with reference to a first embodiment shown in FIG.

In this first embodiment, a variable displacement pump 2 driven by an engine IK and oil discharged from the variable displacement pump 2 are divided into a first pipe line 4 and a second pipe line 5, and A 70-divider 25 having a throttle 3 on the first pipe line 4 side, a power steering cylinder 14 connected to the first pipe line 4 via a power steering switching valve 15, and a working switching valve on the second pipe line 5. In a hydraulic circuit having a tilt cylinder 6a and a lift cylinder 6b connected via cylinders 7m and 7b, a servo motor 9 is installed at one end of the cam plate 2a of the variable displacement pump 2 to control the tilt angle of the pump 2. Connect the second
A flow meter 26 with a transmitter is inserted in the pipeline connecting the first port 7a1 on the outlet side of the switching valves 7a, 7b and the tank 11, and the rotation speed signal of the flow meter 26, that is, the variable displacement pump 20 A computing unit 28 is provided which inputs the surplus flow rate signal, amplifies it, and generates a drive signal for the servo motor 9, that is, a tilt angle increase/decrease signal for the variable displacement pump 2.

Since the first embodiment has the above-described configuration, the servo motor 9Fi cam plate 2a is initially held in a position where it has been moved to the left end in FIG. 2, and the pump inclination angle is at its maximum. When the engine 1 is rotated, the variable displacement pump 2 is driven. When the switching valves 15°7m and 7b are not operated and they are in the neutral state, the oil discharged from the pump 2 flows into the tank 11 through the throttle 3, and the pressure control valve 17 is activated by the differential pressure generated across the throttle 3. Operate. As a result, a portion of the pump discharge oil flows into the second pipe 5. It flows into the flow meter 26 via the first port 7al of the switching valves 7a, 7b and the fourth pipe line 8, and generates a surplus flow signal. The fluid flowing out from the flow meter 26 is released into the tank 11. The surplus flow rate signal is input to the calculator 28, and the output signal that has been amplified by calculation is applied to the servo motor 9, which rotates the cam plate 2a clockwise to reduce the pump inclination angle, thereby adjusting the pump discharge amount to the required minimum flow rate. to control.

The power steering cylinder 14 is operated by operating the switching valve 15 during traveling. At this time, the oil discharged from the pump 2 is supplied to the power steering cylinder 14 for several seconds 3, and the pressure at both ends of the throttle 30 increases, but since the differential pressure is constant, the magnitude of the signal from the flowmeter 26 does not change. figure,
The pump discharge amount is controlled to a constant required minimum flow rate regardless of the engine speed.

During work, the switching valves 7a and 7b are switched from the neutral position to the operating position to supply part of the oil discharged from the pump 2 to the tilt cylinder 6a and lift cylinder 6b, and return the return oil from the cylinders to the tank 11. The tilt cylinder 6a and lift cylinder 6b are operated. The operation of the lift cylinder 6b in this case is an operation for raising the elevator of the forklift. At this time, since communication with the second pipe line 5 and the fourth pipe line 8 is cut off, the value of the surplus flow signal of the flow meter 26 becomes smaller, and the calculator 28 outputs an inclination angle increase signal to the servo motor 9. The cam plate 2ad is rotated counterclockwise, the pump inclination angle becomes maximum, and the pump discharge amount is controlled to the maximum flow rate according to the rotation speed of the engine 1.

Note that when the busy switching valve 7b is operated to lower the elevator of the forklift, the lift cylinder 6b is not operated by the supply of pump discharge oil but by the load of the elevator, so in this case, the lift cylinder 6b is operated by the load of the elevator. The second conduit 5#'i communicates with the fourth conduit 8 in the same way as when drinking or driving, and controls the pump discharge amount to the required minimum flow rate.

As described above, according to the first embodiment, the discharge amount of the variable displacement pump can be controlled to the required minimum flow rate regardless of the engine speed when idling or driving, thereby minimizing energy loss. Moreover, when working by supplying pump discharge oil, the pump discharge amount can be controlled to the maximum flow rate according to the engine rotation speed, so that one work can be carried out efficiently.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

The servo motor 9 is constructed of a hydraulic cylinder 9a connected to one end of the cam plate 2a, and an electromagnetic valve 9b which receives a signal from the computing unit 28 and controls the hydraulic cylinder 9a. Part of the pump discharge oil may be used as the operating fluid for the solenoid valve 9b.

In addition, as shown in the third figure, the variable displacement pump 20 cam plate 2 &
A pressure meter 29 is connected to the other end, and a fifth pipe 13 branched from the pump discharge pipe 10 is connected to a pressure detector 12.
The signal from the pressure detector 12 and the signal from the potentiometer 29 are each applied to a computing unit 28 for operational amplification, and the output signal is applied to the servo motor 9 to perform horsepower control. is possible.

That is, potentiometer 29, pressure detector 12. The computing unit 28 and the servo motor 9 form a horsepower limiting device, and the computing unit 28 and the servo motor 9 also serve as elements of the constant discharge amount control device.

Second Embodiment Since the configuration is as described above, the hydraulic cylinder 9a of the servo motor 9 is first! The cam plate 2a is held at a position moved to the left as far as the left end in Figure 3, and the pump inclination angle becomes maximum b. When the engine 1 is rotated, the variable displacement pump 2 is driven. KF at idle link when switching valves 15.7m and 7b are not operated and both are in the neutral state.
i The oil discharged from pump 2 flows into tank IIK through throttle b3.

The pressure control valve 17 is actuated by the differential pressure generated across the throttle 3. As a result, a part of the pump discharge oil was transferred to the second pipe line 5゜switching valve 7m.
, 7b flows into the flowmeter 26 via the first boat 7ml and the fourth conduit 8, and generates a surplus flow signal. The fluid Fi tank IIK flowing out from the flow meter 26 is opened. The surplus flow rate signal is input to the calculator 28, and the amplified output signal is applied to the servo motor 9 to rotate the cam plate 2a clockwise to reduce the pump inclination angle and reduce the pump discharge amount to the required minimum flow rate. Control.

When traveling, the switching valve 15 is operated to operate the power steering link cylinder 14. At this time, the oil discharged from the power steering cylinder 141C pump 2 is supplied through the throttle 3, and the pressure at both ends of the throttle 30 increases, but since the differential pressure is constant, the magnitude of the signal from the flow meter 26 does not change. , the pump discharge amount is controlled to a constant required minimum flow rate regardless of the rotation speed of the engine 1.

During work, switch the switching valves 7m and 7b from the neutral position to the operating position to supply part of the oil discharged from the pump 2 to the tilt cylinder 6a and 7 cylinder 6b, and return the return oil from the # cylinder to the tank 11. The tilt cylinder 6a and lift cylinder 6b are operated. The operation of the lift cylinder 6b in this case is an operation for raising the elevator of the forklift. At this time, communication with the fifth second pipe line 8 and the fourth pipe line 8 is cut off, so the value of the surplus flow signal of the flow meter 26 decreases to a small value, and an inclination angle increase signal is output to the calculator 28Fi servo motor 9. The cam plate 2a is rotated counterclockwise,
The pump inclination angle is set to the maximum, and the pump discharge amount is controlled to the maximum flow rate according to the rotational speed of the engine 1. However, in this second embodiment, while the pump pressure during Fi1 work is detected by the pressure detection (to) 12 via the pipe 13, the pump inclination angle is detected by the potentiometer 29, and these The signal is added to the calculator 28,
The horsepower consumption of the pump is controlled so as not to exceed a certain limit. That is, when the product of both signals exceeds a certain value, the calculator 28 generates a signal to reduce the pump inclination angle to limit the horsepower.

As mentioned above, the second impeding method not only has the same effect as the first impeding method but also has a horsepower limiting function, so that the load increases and exceeds the engine output. - When this happens, the horsepower limiting mechanism is immediately activated and the pump discharge amount can be reduced to the flow rate corresponding to the maximum engine output, and the engine will not stop. Needless to say, the present invention can be applied not only to a loader but also to a loader and the like.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional device, FIG. 2 is a circuit diagram showing a first embodiment of the device of the present invention, and FIG. 3 is a circuit diagram showing a second embodiment of the device of the present invention. 1・・・・・・・・・Engine, 2・・・・・・・・・
Variable displacement pump. 2a...I...Cam plate, 3......
Aperture, 4......First conduit, 5...
...Second pipe line, 6a...Tilt cylinder (second actuator), 6b...
Lift cylinder (second actuator)%7&,7b
...... Work switching valve (second switching valve), 7
ml・・・・・・・・・1st port, 8・・・・・・・・・
...4th conduit, 9... Servo motor, 9
Todoroki......Hydraulic cylinder, 9b...
...Solenoid valve, 10...Pump discharge pipe, 11...Tank, 14...
...Power steering cylinder, 15...
... Power steering switching valve (first switching valve), 2
5・・・・・・・・・Floater/(Ida, 26・・・・
...Flow rate needle, 28 ......Arithmetic unit. Patent applicant: Japan Steel Works, Ltd.

Claims (2)

[Claims] (1) Variable displacement pump driven by an engine,
A flow divider which divides the discharge oil of the variable displacement pump into the first pipe line and the second pipe line and has several seconds on the first pipe line side, and a first switching valve in the first pipe line. 1st connected
and an actuator llI2 connected to the second pipe line via a second switching valve, which is connected to one end of the cam plate of a variable displacement pump and controls the inclination angle of the pump. It is equipped with a servo motor to control and a flow rate needle with a transmitter inserted in the pipeline connecting the first port on the outlet side of the second switching valve and the tank, and uses the signal from the flow rate needle as input to perform operational amplification. 1. A hydraulic control device comprising a computing unit that outputs an operation signal for a servo motor. (2) The hydraulic control device according to claim 1, wherein the servo motor includes a hydraulic cylinder and a solenoid valve that controls the hydraulic cylinder.